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<p align="center"><font face="Verdana, Arial, Helvetica, sans-serif" color="#666666" size="2">  <font size="3"><b><font color="#0000CC">FIELDBUS</font></b></font></font></p>
<p align="center"><font face="Verdana, Arial, Helvetica, sans-serif" color="#666666" size="-2">Information 
  supplied by courtesy of <b><a href="http://www.industrialnetworking.co.uk/" target="_top">Industrial 
  Networking and Open Control,</a></b></font><font face="Verdana, Arial, Helvetica, sans-serif" color="#666666" size="2"><br>
  <br>
<font size="3"><b>Which Fieldbus to go for?</b></font></font></p>
<p><font face="Verdana, Arial, Helvetica, sans-serif" color="#666666" size="2"> 
  There have emerged literally hundreds of fieldbuses developed by different companies 
  and organisations all over the world. The term fieldbus covers many different 
  industrial network protocols. Most fieldbus protocols have been developed and 
  supported by specific PLC manufacturers. The accompanying table summarises some 
  of the main ones.</font></p>
<p><font face="Verdana, Arial, Helvetica, sans-serif" color="#666666" size="2"> 
  At the lowest level are the sensor networks, which were originally designed 
  primarily for digital (on/off) interface. These are fast and effective, but 
  with only limited applications beyond relatively simple machine-control. ASI 
  (actuator/sensor interface) is popular in Europe, while Seriplex is a US development. 
  ASI - perhaps the simplest and least expensive fieldbus. ASI was developed by 
  a consortium of European automation companies, which saw need for networking 
  the simplest devices at the lowest level. ASI is easy to configure and low in 
  cost. It is most often used for proximity sensors, photoeyes, limit switches, 
  valves and indicators in applications like packaging machines and material handling 
  systems. ASI is designed for small systems employing discrete I/O. It allows 
  for up to 31 slaves, which can provide for up to four inputs and four outputs 
  each for a total of 248 I/O. </font></p>
<p><font face="Verdana, Arial, Helvetica, sans-serif" color="#666666" size="2">Filbus 
  was developed by GESPAC as a comprehensive remote I/O system, based on distributed 
  intelligence and peer-to-peer communication. Firmware functions are built into 
  each Filbus I/O module and allow basic capabilities such as pulse count, delay 
  before action and sending/receiving messages to/from other modules on the network.</font></p>
<p><font face="Verdana, Arial, Helvetica, sans-serif" color="#666666" size="2"> 
  Bitbus was originally introduced by Intel as a way to add remote I/O capability 
  to Multibus systems. This original fieldbus is one of the most mature and most 
  broadly used networks today. Bitbus allows programs to be downloaded and executed 
  in a remote node for truly distributed system configurations. </font></p>
<p><font face="Verdana, Arial, Helvetica, sans-serif" color="#666666" size="2">WorldFIP 
  provides a deterministic and reliable scheme for communicating process variables 
  (generated by sensors and executed by actuators) and messages (events, configuration 
  commands) at up to 1Mbit per second on inexpensive twisted pairs cables. FIP 
  uses an original mechanism where the bus arbitrator broadcasts a variable identifier 
  to all nodes on the network, triggering the mode producing that variable to 
  place its value on the network. Once on the network, all modules which need 
  that information "consume" it simultaneously. This concept results in a decentralised 
  database of variables in the nodes and remarkable real-time characteristics. 
  This feature eliminates the notion of node address and makes it possible to 
  design truly distributed process control systems.</font></p>
<p><font face="Verdana, Arial, Helvetica, sans-serif" color="#666666" size="2"> 
  At the next level are the device buses, which provide analogue and digital support 
  for more complex instruments and products. <b><a href="http://www.odva.org/" target="_blank">DeviceNet</a></b> 
  interfaces very well with programmable controllers. However, it is still only 
  a local, device-level network, operating typically with up to 64 points within 
  about 300m. Profibus DP and Interbus are somewhat comparable to DeviceNet and 
  are excellent general-purpose device-level networks.</font></p>
<p><font face="Verdana, Arial, Helvetica, sans-serif" color="#666666" size="2"> 
  <b><a href="http://www.profibus.com/" target="_blank">Profibus</a></b> is a fieldbus network 
  designed for deterministic communication between computers and PLCs. It is the 
  most widely accepted international networking standard. Nearly universal in 
  Europe and also popular in North America, South America and parts of Africa 
  and Asia, Profibus can handle large amounts of data at high speed and serve 
  the needs of large installations. Based on a real-time capable asynchronous 
  token bus principle, Profibus defines multi-master and master-slave communication 
  relations, with cyclic or acyclic access, allowing transfer rates of up to 500kbit/s. 
  The physical layer (two-wire RS485), the data link layer 2 and the application 
  layer are all standardised. Profibus distinguishes between confirmed and unconfirmed 
  services, allowing process communication, broadcast and multi-tasking. Profibus 
  DP is a master/slave polling network with the ability to upload/download configuration 
  data and precisely synchronise multiple devices on the network. Multiple masters 
  are possible in Profibus, but the outputs of any device can only be assigned 
  to one master. There is no power on the bus. </font></p>
<p><font face="Verdana, Arial, Helvetica, sans-serif" color="#666666" size="2"><a href="http://www.interbusclub.com/" target="_blank"><b>Interbus</b></a> 
  was one of the very first Fieldbuses to achieve widespread popularity. It continues 
  to be popular because of its versatility, speed, diagnostic and auto-addressing 
  capabilities. Physically, it has the appearance of being a typical line-and-drop 
  based network, but in reality it is a serial ring shift register. Each slave 
  node has two connectors, one which receives data and one which passes data onto 
  the next slave. </font></p>
<p><font face="Verdana, Arial, Helvetica, sans-serif" color="#666666" size="2">Controller 
  Area Network (CAN) is a fast serial bus that is designed to provide an efficient, 
  reliable and very economical link between sensors and actuators. CAN uses a 
  twisted pair cable to communicate at speeds up to 1Mbit/s with up to 40 devices. 
  Originally developed to simplify the wiring in automobiles, its use has spread 
  in machine and factory automation products. CAN provides standardised communication 
  objects for process data, service data, network management, synchronisation, 
  time-stamping and emergency messages. It is the basis of several sensor buses, 
  such as DeviceNet (Allen-Bradley), Honeywell's SDS or Can Application Layer 
  (CAL) from CAN in Automation, group of international users and manufacturers, 
  which is over 300 companies strong. CANOpen is a family of profiles based on 
  CAN which was developed within the CAN in Automation group. The extensive error 
  detection and correction features of CAN can easily withstand the harsh physical 
  and electrical environment presented by a car. SDS was developed by Bosch for 
  networking most of the distributed electrical devices throughout an automobile, 
  initially for eliminating the large and expensive wiring harnesses in Mercedes. 
  </font></p>
<p><font face="Verdana, Arial, Helvetica, sans-serif" color="#666666" size="2">DeviceNet 
  is a manifestation of CAN adapted for critical factory networking purposes. 
  At the next level are the "control" networks, which include ControlNet, developed 
  by Allen-Bradley and utilised by Honeywell, overlapping with some of the functionality 
  intended to be provided by Profibus-FMS and Fieldbus SP-50 - Profibus FMS uses 
  the same physical layer as Profibus DP but allows multi-master, asynchronous, 
  peer-to-peer communication. FMS and DP can operate simultaneously on the same 
  network. ControlNet was conceived as the ultimate high-level fieldbus network 
  and was designed to meet several high performance automation and process control 
  criteria. Of primary importance is the ability to communicate with each other 
  with 100% determinism, while achieving faster response than traditional master/slave 
  poll/strobe networks.</font></p>
<p><font face="Verdana, Arial, Helvetica, sans-serif" color="#666666" size="2"> 
  LONWorks operates over greater distances and is a practical peer-to-peer network, 
  extensible to many thousands of points, though it can be comparatively slow 
  and more complex. Profibus PA is a specification for using Profibus in intrinsically 
  safe applications. It provides improved performance at the fieldbus level, for 
  instruments and controls, replacing the features and functions which are provided 
  by HART, originally developed for transmitter calibration and diagnostics. The 
  primary differences are in speed, complexity and distance. LONWorks also extends 
  into this realm.</font></p>
<p><font face="Verdana, Arial, Helvetica, sans-serif" color="#666666" size="2"> 
  Foundation Fieldbus is a sophisticated, object-oriented protocol that uses multiple 
  messaging formats and allows a controller to recognize a rich set of configuration 
  and parameter information ("device description") from devices that have been 
  plugged into the bus. Foundation Fieldbus even allows a device to transmit parameters 
  relating to the estimated reliability of a particular piece of data. Foundation 
  Fieldbus uses a scheduler to guarantee the delivery of messages, so issues of 
  determinism and repeatability are solidly addressed (determinism means knowing 
  absolute worst-case response times with 100% certainty). Each segment of the 
  network contains one scheduler. </font></p>
<p><font face="Verdana, Arial, Helvetica, sans-serif" color="#666666" size="2">In 
  the United States, DeviceNet, Profibus DP, and Foundation Fieldbus H1 have taken 
  their places as the dominant open systems for connecting industrial devices. 
  DeviceNet is the leader in automotive, materials handling, and semiconductor 
  applications, while Foundation Fieldbus is taking the lead in process control. 
  Profibus is strong in both realms, as well as being the dominant technology 
  in Europe. </font></p>
<p><font face="Verdana, Arial, Helvetica, sans-serif" color="#666666" size="2">Since 
  its introduction, DeviceNet has grown rapidly in the UK and, according to DeviceNet 
  UK Chairman Richard McLaughlin, now boasts more than 320 companies worldwide 
  actively developing compatible products within the Open DeviceNet Vendor Association 
  (ODVA). These include sensors, actuators and smart devices.</font></p>
<p><font face="Verdana, Arial, Helvetica, sans-serif" color="#666666" size="2"> 
  Against this backdrop, frustrating for many, came the re-emergence of the Ethernet. 
  Ten years ago, no serious design engineer would have suggested using Ethernet 
  for networking factory floor devices. Ethernet, the technology for office automation, 
  was developed more than 20 years ago as a high-speed serial data-transfer network. 
  It has become a worldwide standard and is now the most widely used Local Area 
  Network (LAN) in existence. More than 85% of all installed network connections 
  in the world are Ethernet. But it was deliberately ignored for industrial applications, 
  and for good reasons; its lack of determinism and robustness made it a feeble, 
  unpredictable companion for the shop floor. Yet today, the scene has almost 
  reversed. Why such a radical change? Over the past few years there have been 
  many enhancements to the Ethernet standard, especially in areas of determinism, 
  speed, and message prioritisation. So there is no longer any reason why Ethernet 
  cannot be used to build deterministic fieldbus networks that are cost-effective 
  and open. And since Ethernet is already the network choice for business computing, 
  its presence at the control level will make sensor-to-boardroom integration 
  a reality. Another good reason manufacturers are looking at Ethernet is the 
  coming explosion of factory floor data traffic. As smart sensors and various 
  devices on the plant floor eat up the available bandwidth over the next four 
  years, manufacturing plant information generated by PLCs and control systems 
  is expected to increase from 10 to 30 times the current level. Ethernet, with 
  its Internet-friendly TCP/IP protocol, is ideally positioned. It is popular, 
  plummeting in price and being propelled by sheer market demand.</font></p>
<p><font face="Verdana, Arial, Helvetica, sans-serif" color="#666666" size="2"> 
  So Ethernet is poised to penetrate deep into the factory network hierarchy, 
  down to the I/O level. That makes some programmable controller (PLC) manufacturers 
  uncomfortable. Even the recently arrived fieldbus systems are beginning to feel 
  the impact - some say threat - of Ethernet. Furthermore, the DeviceNet, Profibus 
  and Foundation Fieldbus protocols are all available or in development as application 
  layers for Ethernet. And most PLCs now offer Ethernet as a standard networking 
  option in addition to their fieldbus of choice. High Speed Ethernet (HSE) is 
  a 100 Mbit Ethernet standard that uses the same protocol and objects as Foundation 
  Fieldbus H1, on TCP/IP. The next generation of Ethernet is called Gigabit Ethernet, 
  which is capable of 1 Gbits/sec). This will bridge the gap between the necessity 
  of industrially hardened wiring capability and the growing need for process 
  data via business LANs and the Internet. Most firms cannot afford to have a 
  DeviceNet or Profibus specialist on staff who thoroughly understands the network 
  protocol. Even if a company could afford such a person, it is unlikely fieldbus 
  would be their specialty. However, almost every company has a network administrator 
  who is well versed and specialises in Ethernet protocol, making Ethernet all 
  the more attractive for industrial control. </font></p>
<p><font face="Verdana, Arial, Helvetica, sans-serif" color="#666666" size="2"> 
  Quote: "<i>Industrialists have the expectation in mind that they can use Ethernet, 
  that they are going to use it, and application barriers that present themselves 
  can be worked through. Manufacturers are pressing for an Ethernet Plan. Industrial 
  Ethernet will happen, and it will only be a spirited marketplace standardisation 
  shakeout, combined with badly needed guidance from the Industrial Ethernet Association 
  (IEA) that remain to complete its destiny</i>." Lance Gordon, Senior Analyst, 
  Frost &amp; Sullivan <br>
  </font></p>
<table border="" bordercolor="#666666">
  <tbody><tr> 
    <td valign="bottom" nowrap="" width="151"><b><font face="Verdana, Arial, Helvetica, sans-serif" size="2" color="#000099">Fieldbus 
      Comparison Chart</font></b></td>
  </tr>
  <tr></tr>
  <tr bgcolor="#CCCCFF" bordercolor="#999999"> 
    <td valign="bottom" nowrap="" width="151" height="17"><b><font face="Verdana, Arial, Helvetica, sans-serif" size="2">Fieldbus</font></b></td>
    <td valign="bottom" nowrap="" width="131" height="17"><b><font face="Verdana, Arial, Helvetica, sans-serif" size="2">Technology</font></b></td>
    <td valign="bottom" nowrap="" width="122" height="17"><b><font face="Verdana, Arial, Helvetica, sans-serif" size="2">Year</font></b></td>
    <td valign="bottom" nowrap="" width="225" height="17"><b><font face="Verdana, Arial, Helvetica, sans-serif" size="2">Physical 
      </font></b></td>
    <td valign="bottom" nowrap="" width="142" height="17"><b><font face="Verdana, Arial, Helvetica, sans-serif" size="2">Max 
      Devices</font></b></td>
    <td valign="bottom" nowrap="" width="107" height="17"><b><font face="Verdana, Arial, Helvetica, sans-serif" size="2">Max 
      Distance</font></b></td>
    <td valign="bottom" nowrap="" width="308" height="17"><b><font face="Verdana, Arial, Helvetica, sans-serif" size="2">Primary</font></b></td>
  </tr>
  <tr bgcolor="#CCCCFF" bordercolor="#999999"> 
    <td valign="bottom" nowrap="" width="151"><b><font face="Verdana, Arial, Helvetica, sans-serif" size="2">Name</font></b></td>
    <td valign="bottom" nowrap="" width="131"><b><font face="Verdana, Arial, Helvetica, sans-serif" size="2">Developer</font></b></td>
    <td valign="bottom" nowrap="" width="122"><b><font face="Verdana, Arial, Helvetica, sans-serif" size="2">Introduced</font></b></td>
    <td valign="bottom" nowrap="" width="225"><b><font face="Verdana, Arial, Helvetica, sans-serif" size="2">Media</font></b></td>
    <td valign="bottom" nowrap="" width="142"><b><font face="Verdana, Arial, Helvetica, sans-serif" size="2">Nodes</font></b></td>
    <td valign="bottom" nowrap="" width="107"><b><font face="Verdana, Arial, Helvetica, sans-serif" size="2">(typical)</font></b></td>
    <td valign="bottom" nowrap="" width="308"><b><font face="Verdana, Arial, Helvetica, sans-serif" size="2">Applications</font></b></td>
  </tr>
  <tr></tr>
  <tr> 
    <td valign="bottom" nowrap="" width="151"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">Profibus 
      DP/PA</font></td>
    <td valign="bottom" nowrap="" width="131"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">Siemens</font></td>
    <td valign="bottom" nowrap="" width="122"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">DP: 
      1994 PA: 1995</font></td>
    <td valign="bottom" nowrap="" width="225"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">Twisted 
      pair or fibre</font></td>
    <td valign="bottom" nowrap="" width="142"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">32 
      without repeaters</font></td>
    <td valign="bottom" nowrap="" width="107"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">200m</font></td>
    <td valign="bottom" nowrap="" width="308"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">Inter-PLC 
      communication</font></td>
  </tr>
  <tr> 
    <td width="151"><font size="2"></font></td>
    <td width="131"><font size="2"></font></td>
    <td width="122"><font size="2"></font></td>
    <td width="225"><font size="2"></font></td>
    <td valign="bottom" nowrap="" width="142"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">127 
      with repeaters</font></td>
    <td valign="bottom" nowrap="" width="107"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">800m</font></td>
    <td valign="bottom" nowrap="" width="308"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">Factory 
      automation</font></td>
  </tr>
  <tr></tr>
  <tr> 
    <td valign="bottom" nowrap="" width="151" bgcolor="#FFCCCC"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">Interbus-S</font></td>
    <td valign="bottom" nowrap="" width="131" bgcolor="#FFCCCC"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">Phoenix 
      Contact</font></td>
    <td valign="bottom" nowrap="" width="122" bgcolor="#FFCCCC"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">1984</font></td>
    <td valign="bottom" nowrap="" width="225" bgcolor="#FFCCCC"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">Twisted 
      pair, fibre, slip ring</font></td>
    <td valign="bottom" nowrap="" width="142" bgcolor="#FFCCCC"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">256</font></td>
    <td valign="bottom" nowrap="" width="107" bgcolor="#FFCCCC"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">400m</font></td>
    <td valign="bottom" nowrap="" width="308" bgcolor="#FFCCCC"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">Assembly, 
      welding and materials handling machines</font></td>
  </tr>
  <tr> 
    <td width="151" bgcolor="#FFCCCC"><font size="2"></font></td>
    <td valign="bottom" nowrap="" width="131" bgcolor="#FFCCCC"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">Interbus 
      Club</font></td>
  </tr>
  <tr></tr>
  <tr> 
    <td valign="bottom" nowrap="" width="151"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">DeviceNet</font></td>
    <td valign="bottom" nowrap="" width="131"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">Allen-Bradley</font></td>
    <td valign="bottom" nowrap="" width="122"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">1994</font></td>
    <td valign="bottom" nowrap="" width="225"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">Twisted 
      pair for signal and power</font></td>
    <td valign="bottom" nowrap="" width="142"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">64</font></td>
    <td valign="bottom" nowrap="" width="107"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">500m</font></td>
    <td valign="bottom" nowrap="" width="308"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">Assembly, 
      welding and materials handling machines</font></td>
  </tr>
  <tr></tr>
  <tr> 
    <td valign="bottom" nowrap="" width="151" bgcolor="#FFCCCC"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">Arcnet</font></td>
    <td valign="bottom" nowrap="" width="131" bgcolor="#FFCCCC"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">Datapoint</font></td>
    <td valign="bottom" nowrap="" width="122" bgcolor="#FFCCCC"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">1977</font></td>
    <td valign="bottom" nowrap="" width="225" bgcolor="#FFCCCC"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">Coax, 
      twisted pair, fibre</font></td>
    <td valign="bottom" nowrap="" width="142" bgcolor="#FFCCCC"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">255</font></td>
    <td valign="bottom" nowrap="" width="107" bgcolor="#FFCCCC"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">400-2000 
      feet</font></td>
  </tr>
  <tr></tr>
  <tr> 
    <td valign="bottom" nowrap="" width="151"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">AS-I</font></td>
    <td valign="bottom" nowrap="" width="131"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">AS-I 
      Consortium</font></td>
    <td valign="bottom" nowrap="" width="122"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">1993</font></td>
    <td valign="bottom" nowrap="" width="225"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">Two 
      wire cable</font></td>
    <td valign="bottom" nowrap="" width="142"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">31 
      slaves</font></td>
    <td valign="bottom" nowrap="" width="107"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">100-300m</font></td>
    <td valign="bottom" nowrap="" width="308"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">Assembly, 
      packaging and materials handling machines</font></td>
  </tr>
  <tr></tr>
  <tr> 
    <td valign="bottom" nowrap="" width="151" bgcolor="#FFCCCC"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">Foundation 
      Fieldbus H1</font></td>
    <td valign="bottom" nowrap="" width="131" bgcolor="#FFCCCC"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">Fieldbus 
      Foundation</font></td>
    <td valign="bottom" nowrap="" width="122" bgcolor="#FFCCCC"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">1995</font></td>
    <td valign="bottom" nowrap="" width="225" bgcolor="#FFCCCC"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">Twisted 
      pair, fibre</font></td>
    <td valign="bottom" nowrap="" width="142" bgcolor="#FFCCCC"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">240/segment</font></td>
    <td valign="bottom" nowrap="" width="107" bgcolor="#FFCCCC"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">1900m</font></td>
  </tr>
  <tr> 
    <td width="151" bgcolor="#FFCCCC"><font size="2"></font></td>
    <td width="131" bgcolor="#FFCCCC"><font size="2"></font></td>
    <td width="122" bgcolor="#FFCCCC"><font size="2"></font></td>
    <td width="225" bgcolor="#FFCCCC"><font size="2"></font></td>
    <td valign="bottom" nowrap="" width="142" bgcolor="#FFCCCC"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">65,000 
      segments</font></td>
  </tr>
  <tr></tr>
  <tr> 
    <td valign="bottom" nowrap="" width="151"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">Foundation 
      Fieldbus HSE</font></td>
    <td valign="bottom" nowrap="" width="131"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">Fieldbus 
      Foundation</font></td>
    <td valign="bottom" nowrap="" width="122"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">Current</font></td>
    <td valign="bottom" nowrap="" width="225"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">Twisted 
      pair, fibre</font></td>
    <td valign="bottom" nowrap="" width="142"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">IP 
      addressing</font></td>
    <td valign="bottom" nowrap="" width="107"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">100-2000m</font></td>
  </tr>
  <tr> 
    <td width="151"><font size="2"></font></td>
    <td width="131"><font size="2"></font></td>
    <td width="122"><font size="2"></font></td>
    <td width="225"><font size="2"></font></td>
    <td valign="bottom" nowrap="" width="142"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">essentially 
      unlimited</font></td>
  </tr>
  <tr></tr>
  <tr> 
    <td valign="bottom" nowrap="" width="151" bgcolor="#FFCCCC"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">IEC/ISA 
      SP50 Fieldbus</font></td>
    <td valign="bottom" nowrap="" width="131" bgcolor="#FFCCCC"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">ISA 
      &amp; Fieldbus Foundation</font></td>
    <td valign="bottom" nowrap="" width="122" bgcolor="#FFCCCC"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">1992-1996</font></td>
    <td valign="bottom" nowrap="" width="225" bgcolor="#FFCCCC"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">Twisted 
      pair, fibre, and radio</font></td>
    <td valign="bottom" nowrap="" width="142" bgcolor="#FFCCCC"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">IS: 
      3-7; non-IS 128</font></td>
    <td valign="bottom" nowrap="" width="107" bgcolor="#FFCCCC"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">500-1700m</font></td>
  </tr>
  <tr></tr>
  <tr> 
    <td valign="bottom" nowrap="" width="151" height="18"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">Seriplex</font></td>
    <td valign="bottom" nowrap="" width="131" height="18"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">APC</font></td>
    <td valign="bottom" nowrap="" width="122" height="18"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">1990</font></td>
    <td valign="bottom" nowrap="" width="225" height="18"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">4-wire 
      shielded cable</font></td>
    <td valign="bottom" nowrap="" width="142" height="18"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">500+ 
      devices</font></td>
    <td valign="bottom" nowrap="" width="107" height="18"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">&gt;500 
      feet</font></td>
  </tr>
  <tr></tr>
  <tr> 
    <td valign="bottom" nowrap="" width="151" bgcolor="#FFCCCC"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">WorldFIP</font></td>
    <td valign="bottom" nowrap="" width="131" bgcolor="#FFCCCC"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">WorldFIP</font></td>
    <td valign="bottom" nowrap="" width="122" bgcolor="#FFCCCC"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">1988</font></td>
    <td valign="bottom" nowrap="" width="225" bgcolor="#FFCCCC"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">Twisted 
      pair, fibre</font></td>
    <td valign="bottom" nowrap="" width="142" bgcolor="#FFCCCC"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">64 
      without repeaters</font></td>
    <td valign="bottom" nowrap="" width="107" bgcolor="#FFCCCC"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">2 
      km</font></td>
    <td valign="bottom" nowrap="" width="308" bgcolor="#FFCCCC"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">Real-time 
      control, process/machine</font></td>
  </tr>
  <tr> 
    <td width="151" bgcolor="#FFCCCC"><font size="2"></font></td>
    <td width="131" bgcolor="#FFCCCC"><font size="2"></font></td>
    <td width="122" bgcolor="#FFCCCC"><font size="2"></font></td>
    <td width="225" bgcolor="#FFCCCC"><font size="2"></font></td>
    <td valign="bottom" nowrap="" width="142" bgcolor="#FFCCCC"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">256 
      with repeaters</font></td>
    <td valign="bottom" nowrap="" width="107" bgcolor="#FFCCCC"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">&gt;10 
      km</font></td>
  </tr>
  <tr></tr>
  <tr> 
    <td valign="bottom" nowrap="" width="151"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">LONWorks</font></td>
    <td valign="bottom" nowrap="" width="131"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">Echelon</font></td>
    <td valign="bottom" nowrap="" width="122"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">1991</font></td>
    <td valign="bottom" nowrap="" width="225"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">Twisted 
      pair, fibre, power line</font></td>
    <td valign="bottom" nowrap="" width="142"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">32,000 
      per domain</font></td>
    <td valign="bottom" nowrap="" width="107"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">2000m</font></td>
  </tr>
  <tr></tr>
  <tr> 
    <td valign="bottom" nowrap="" width="151" bgcolor="#FFCCCC"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">SDS</font></td>
    <td valign="bottom" nowrap="" width="131" bgcolor="#FFCCCC"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">Honeywell</font></td>
    <td valign="bottom" nowrap="" width="122" bgcolor="#FFCCCC"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">1994</font></td>
    <td valign="bottom" nowrap="" width="225" bgcolor="#FFCCCC"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">Twisted 
      pair for signal and power</font></td>
    <td valign="bottom" nowrap="" width="142" bgcolor="#FFCCCC"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">64 
      nodes, 126 addresses</font></td>
    <td valign="bottom" nowrap="" width="107" bgcolor="#FFCCCC"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">500m</font></td>
    <td valign="bottom" nowrap="" width="308" bgcolor="#FFCCCC"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">Assembly, 
      materials handling, packaging, sortation</font></td>
  </tr>
  <tr></tr>
  <tr> 
    <td valign="bottom" nowrap="" width="151"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">ControlNet</font></td>
    <td valign="bottom" nowrap="" width="131"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">Allen-Bradley</font></td>
    <td valign="bottom" nowrap="" width="122"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">1996</font></td>
    <td valign="bottom" nowrap="" width="225"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">Coax, 
      fibre</font></td>
    <td valign="bottom" nowrap="" width="142"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">99</font></td>
    <td valign="bottom" nowrap="" width="107"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">250-1000m</font></td>
    <td valign="bottom" nowrap="" width="308"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">Mission-critical, 
      plant-wide networking of PCs, PLCs </font></td>
  </tr>
  <tr></tr>
  <tr> 
    <td valign="bottom" nowrap="" width="151" bgcolor="#FFCCCC"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">CANOpen</font></td>
    <td valign="bottom" nowrap="" width="131" bgcolor="#FFCCCC"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">CAN 
      in Automation</font></td>
    <td valign="bottom" nowrap="" width="122" bgcolor="#FFCCCC"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">1995</font></td>
    <td valign="bottom" nowrap="" width="225" bgcolor="#FFCCCC"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">Twisted 
      pair, optional signal and power</font></td>
    <td valign="bottom" nowrap="" width="142" bgcolor="#FFCCCC"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">30</font></td>
    <td valign="bottom" nowrap="" width="107" bgcolor="#FFCCCC"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">25-1000m</font></td>
    <td valign="bottom" nowrap="" width="308" bgcolor="#FFCCCC"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">Sensors, 
      actuators, automotive</font></td>
  </tr>
  <tr></tr>
  <tr> 
    <td valign="bottom" nowrap="" width="151"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">Industrial 
      Ethernet</font></td>
    <td valign="bottom" nowrap="" width="131"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">DEC, 
      Intel, Xerox</font></td>
    <td valign="bottom" nowrap="" width="122"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">1976</font></td>
    <td valign="bottom" nowrap="" width="225"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">Thin 
      Coax, twisted pair, fibre, thick coax</font></td>
    <td valign="bottom" nowrap="" width="142"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">1024, 
      more via routers</font></td>
    <td valign="bottom" nowrap="" width="107"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">185m 
      (thin)</font></td>
  </tr>
  <tr></tr>
  <tr> 
    <td valign="bottom" nowrap="" width="151" bgcolor="#FFCCCC"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">Modbus 
      Plus</font></td>
    <td valign="bottom" nowrap="" width="131" bgcolor="#FFCCCC"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">Modicon</font></td>
    <td width="122" bgcolor="#FFCCCC"><font size="2"></font></td>
    <td valign="bottom" nowrap="" width="225" bgcolor="#FFCCCC"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">Twisted 
      pair</font></td>
    <td valign="bottom" nowrap="" width="142" bgcolor="#FFCCCC"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">32 
      per segment, 64 max</font></td>
    <td valign="bottom" nowrap="" width="107" bgcolor="#FFCCCC"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">500m 
      per segment</font></td>
  </tr>
  <tr></tr>
  <tr> 
    <td valign="bottom" nowrap="" width="151"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">Modbus 
      RTU/ASCII</font></td>
    <td valign="bottom" nowrap="" width="131"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">Modicon</font></td>
    <td width="122"><font size="2"></font></td>
    <td valign="bottom" nowrap="" width="225"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">Twisted 
      pair</font></td>
    <td valign="bottom" nowrap="" width="142"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">250 
      per segment</font></td>
    <td valign="bottom" nowrap="" width="107"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">350m</font></td>
  </tr>
  <tr></tr>
  <tr> 
    <td valign="bottom" nowrap="" width="151" bgcolor="#FFCCCC"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">Remote 
      I/O</font></td>
    <td valign="bottom" nowrap="" width="131" bgcolor="#FFCCCC"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">Allen-Bradley</font></td>
    <td valign="bottom" nowrap="" width="122" bgcolor="#FFCCCC"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">1980</font></td>
    <td valign="bottom" nowrap="" width="225" bgcolor="#FFCCCC"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">Twinaxial</font></td>
    <td valign="bottom" nowrap="" width="142" bgcolor="#FFCCCC"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">32 
      per segment</font></td>
    <td valign="bottom" nowrap="" width="107" bgcolor="#FFCCCC"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">6km</font></td>
  </tr>
  <tr></tr>
  <tr> 
    <td valign="bottom" nowrap="" width="151"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">Data 
      Highway Plus (DH+)</font></td>
    <td valign="bottom" nowrap="" width="131"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">Allen-Bradley</font></td>
    <td width="122"><font size="2"></font></td>
    <td valign="bottom" nowrap="" width="225"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">Twinaxial</font></td>
    <td valign="bottom" nowrap="" width="142"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">64 
      per segment</font></td>
    <td valign="bottom" nowrap="" width="107"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">3km</font></td>
  </tr>
  <tr></tr>
  <tr bgcolor="#FFCCCC"> 
    <td valign="bottom" nowrap="" width="151"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">Filbus</font></td>
    <td valign="bottom" nowrap="" width="131"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">Gespac</font></td>
    <td width="122"><font size="2"></font></td>
    <td valign="bottom" nowrap="" width="225"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">Twisted 
      pair</font></td>
    <td valign="bottom" nowrap="" width="142"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">32 
      without repeaters</font></td>
    <td valign="bottom" nowrap="" width="107"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">1.2km</font></td>
    <td valign="bottom" nowrap="" width="308"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">Remote 
      I/O, data acquisition</font></td>
  </tr>
  <tr bgcolor="#FFCCCC"> 
    <td width="151"><font size="2"></font></td>
    <td width="131"><font size="2"></font></td>
    <td width="122"><font size="2"></font></td>
    <td width="225"><font size="2"></font></td>
    <td valign="bottom" nowrap="" width="142"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">250 
      with repeaters</font></td>
    <td valign="bottom" nowrap="" width="107"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">13.2 
      km</font></td>
  </tr>
  <tr></tr>
  <tr> 
    <td valign="bottom" nowrap="" width="151"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">Bitbus</font></td>
    <td valign="bottom" nowrap="" width="131"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">Intel</font></td>
    <td width="122"><font size="2"></font></td>
    <td valign="bottom" nowrap="" width="225"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">Twisted 
      pair</font></td>
    <td valign="bottom" nowrap="" width="142"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">32 
      without repeaters</font></td>
    <td valign="bottom" nowrap="" width="107"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">1.2km</font></td>
    <td valign="bottom" nowrap="" width="308"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">Intelligent 
      I/O modules, Process control</font></td>
  </tr>
  <tr> 
    <td width="151"><font size="2"></font></td>
    <td width="131"><font size="2"></font></td>
    <td width="122"><font size="2"></font></td>
    <td width="225"><font size="2"></font></td>
    <td valign="bottom" nowrap="" width="142"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">250 
      with repeaters</font></td>
    <td valign="bottom" nowrap="" width="107"><font face="Verdana, Arial, Helvetica, sans-serif" size="2">13.2 
      km</font></td>
  </tr>
</tbody></table>
<p><font face="Verdana, Arial, Helvetica, sans-serif" color="#666666" size="2"><br>
  Information supplied by courtesy of <b><a href="http://www.industrialnetworking.co.uk/" target="_blank">Industrial 
  Networking and Open Control,</a></b></font></p>
<p>&nbsp;</p>
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